I have seen some "blueish" variants of the burtoni. The leading edge of the pelvic fin will turn black with a blue hue but not the entire fin. Some burtoni's will even exhibit some banding through the body, especially if you turn the tank lights on when the tank is dark. The spotting on the dorsal and tail are the give away.
the OP's fish looks more like a species of tilapia to me... if you wanted my guess, maybe a blackchin? (btw, the only species illegal to keep in the USA is the spotted tilapia, and that may only be in the southern states anyway). he is a pretty fish, and you should keep this updated... he's still young, so i could be wrong...